The invention relates to a device comprising an integrated coil L on a substrate, which coil includes a first conductor track in the form of a spiral having windings, with an outer end of the first track being situated on an outside of the spiral, and an inner end of the first track being situated on an inside of the spiral, and said coil comprising a conductive cross-strip which is connected to the inner end and continues to the outside of the spiral, so that the cross-strip forms a crossing with a winding in the spiral.
Such a device can very suitably be used for applications which, dependent on the frequency of electromagnetic waves, must exhibit a specific response, such as filter devices. In practice, the coil is provided on an insulated, relatively flat substrate, such as a semiconductor substrate provided with switching elements or an insulating substrate. The coil is integrated, that is, the coil is not composed of loose, wound wire but instead is manufactured by means of techniques known from the manufacture of ICs. The coil comprises the first conductor track in the form of a spiral. A problem with such a spiral is that the inner end of the spiral is difficult to contact. For this purpose, use is made of a so-called cross-strip which makes contact with the an outside of the spiral, said cross-strip extending above or below the first conductor track.
The cross-strip is not formed in the same conductive layer as the first conductor track. The crossing between the first conductor track and the cross-strip has a specific capacitance and capacitively couples a point on the first conductor track and the cross-strip to one another. This is undesirable because this coupling adversely affects the frequency characteristic of the device, particularly at high frequencies.
A device of the type mentioned in the opening paragraph is known from the English-language summary of Japanese patent application 62-69545, which device comprises a number of crossings, and, at the location of said crossings, the first track is recessed so that a relatively thick layer of an insulating material can be provided between the cross-strip and the first track without the flatness of the device being influenced excessively. Due to this thick layer, the capacitance between the first track and the cross-strip is only small.
The above-described device in accordance with the prior art has the disadvantage that such a recess is relatively difficult to manufacture. A recess must be made in a substrate. The first track crosses this recess. There is a risk that the first track is locally interrupted or much thinner on the edges of the recess. In addition, it is necessary to provide a thick layer of an insulating material.